Image acquisition devices such as camera modules are commonly integrated into various other mobile computing devices, such as smartphones or tablet computers. Typically, camera modules integrated into mobile computing devices are implemented as one or more substantially cube-like modules. The recent trend of minimizing the width or thickness of the underlying mobile computing devices has resulted in a similar trend of minimizing the height of the integrated camera modules by necessity.
Unfortunately, due the compacted height of the integrated camera modules, the incident light rays at more extreme angles are received, relative to less compact systems. This can result in an undesirable effect (called lens shading) where images are produced with heightened brightness in the center and substantially less brightness towards the edges.
Contemporary photographic techniques have been able to account for, and mitigate this effect. Typically, lens shading corrections are performed by programming coefficients into each manufactured camera module that are subsequently applied to image data. However, since the amount of lens shading is dependent on the source of light (or “illuminant”) detected in the scene (typically determined through a process of white balancing), the amount of programmed coefficients can be significant.
Moreover, actual calculation of the coefficients traditionally requires extensive measurement and calibration specific to each camera module. That is, coefficient determination conventionally requires the generation of several models of camera module “surfaces,” with the actual amount of surfaces corresponding to the number of illuminants that an image can be captured in. Conventional techniques for generating these surfaces include generating a plurality of images with each camera module under a plurality of lighting conditions. This can comprise upwards of ten or more images per module unit, and requires facilities for producing each of the supported lighting conditions. As a result, traditional lens shading calibration techniques can be a very inefficient process, requiring substantially intensive amounts of time and effort, particularly for units that are mass-produced.